Year: 2015

SQL Server Mirroring Related Queries: How do I swap Primary and Secondary on Mirroring Databases ? When the automatic failover is setup , the Primary / Secondary gets swapped during maintenance tasks. To swap back the Primary/Secondary , connect to the…

Highly Scalable Fault Tolerant Scalable Systems Considertions: Dr Tanenbaum on Fault Tolerant Operating Systems. https://en.wikipedia.org/wiki/Andrew_S._Tanenbaum Murphys Law: https://en.wikipedia.org/wiki/Edward_A._Murphy,_Jr. https://en.wikipedia.org/wiki/Murphy%27s_law If there’s more than one possible outcome of a job or tasks and one of those outcome will result in disaster…

We do online assessment and reporting for K-12 Education Industry. ( http://emetric.net/ ). We had a need to load 3 through K-12 students historical test reports for entire state for past 10 + years , which ended up being close to billion rows for historical data.

Highlights: Data Migration Tool – We use aurora and data loading is little more than walk in the park. Hope this solves our problem. QuickSight – Explore this product for our needs RedShift – See how it can cutdown our Data…

Importing and Exporting Data into Amazon RDS We had a business need to load ~ Billion rows of Data into MySQL or Aurora Database. These are the information I gathered on optimizing load process. Load Data Infile Link to MySQL…

Aurora RDS: AWS Released encryption for Aurora Instances. Encryption is not available as of now. Amazon RDS Encryption Links Encrypting Amazon RDS Resources You can encrypt your Amazon RDS instances and snapshots at rest by enabling the encryption option for…

Iworked with CentOS servers from Windows PCs,andIhad the same problem with PuTTY.Asession didn't last more than 1-5 minutes. I tried to play with PuTTY settings (keepalives, etc.) but it didn'thelp at all.

FinallyIhave found the solution formy case.I've recorded TCP dumps both on the client and the server. I've discovered that during25-30seconds before disconnecting there are several retransmissions of TCP segments inthe client's dump (both from the client'sandfrom the server's side) and finally PuTTY sends RST and close the session with that error. In the server'sdumpIdidn't see any segments from the client in this period, even RST. It means that time to time no TCP segments from the client are delivered to the server and this period is about 30-60 seconds. I've recorded the caseseveral times andalways there were retransmissions andfinalRST from PuTTY.Probably somewhere on the route packets were dropped by network equipments.

TomakeaworkaroundI've increased the maximal number of data retransmissions from the default value 5 up to 16. It could prevent PuTTY from disconnection too fast. The variable is 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\TcpMaxDataRetransmissions'. I've added thisvariable manually,it wasn'tinitially defined inthe registy of my Windows.It did help!NowIsee that PuTTY hangs from time totime,but it always comes back.

TempDB contention: TempDB plays very crucial in well performing SQL Server engine. These are few simple design decisions , which helps to avoid the performance bottlenecks in the long run. As a general rule, if the number of logical processors is…

Concurrency and Storage Needs : Requirements: We operate on K-12 Online Summative Market. Our Needs are: When Kids log-in to take the test, they should be able to login without any issues. Should be able to store their responses and…

How to handle Perennial statement of “Our Database is SLOW”? I have been involved with Database and Product Development for a decade in different Verticals. I have heard this statement more than I could count “Database is Slow”,”Database is the…

Random GUID or Sequential GUID SQL Server has two in-built functions for creating uniqueidentifier. NEWID() NEWSEQUENTIALID() New NEWSEQUENTIALID would help to reduce page splits and fragmentation because of sequential nature of the values returned from this function. NEWID() is truly…

More CPU’s in SQL Server : Does it Help or Hurt? (MAXDOP): Common sense tells us , having more CPU’s mean more processing power , that means things would be done faster. Hold on for a sec..Its SQL Server. Common…

MERGE Statement and Deadlocks: We have MERGE SQL Statement to satisfy our functional needs. Instead of writing separate Insert / Update (UPSERT) Statement we decided to use MERGE Statement because of its simplicity in syntax.